Money is important. For a long time, economists thought that it was the only thing that mattered. And, in fact, if you want people to do what you want, money can be incredibly useful. Out to entice the best workers? Pay more. Want to sell a product? Discount it, a lot. Want to discourage a bad behavior? Impose a monetary fine.

It seemed a little silly to us though (as well as to other behavioral economists doing work back in the 1990s) to think that money was the only thing that mattered. So we set out to learn exactly when and how monetary incentives work. Along the way, we discovered some environments where incentives don’t work at all.